Neurotensin (NT) is a tridecapeptide widely distributed in the CNS including the entorhinal cortex (EC) which is crucial for learning and memory and undergoes the earliest pathological alterations in Alzheimer's Disease (AD). Whereas high density of NT receptors has been detected in the EC, the roles of NT in learning and memory and in AD have not been determined. AD is characterized by progressive deterioration of cognitive performance and afflicts ~5.3 million Americans. The current drugs available for the treatment of AD including the cholinesterase inhibitors and the partial NMDA receptor antagonist memantine only benefit a subset of patients for a limited period. Therefore, identifying and characterizing additional mechanisms through which cognitive deficiency can be improved still represent an important approach for AD therapy. We propose to study the roles and the underlying mechanisms of NT in facilitation of spatial memory in the EC and then test the possibility of using NT receptor agonists for AD therapy in AD mouse model. We have substantial preliminary data demonstrating that NT induced Long-Term Excitation (LTE) of neuronal excitability in the EC. We also demonstrated that microinjection of NT into the EC facilitated spatial learning and memory in Barnes Maze Test. The objective of this project is to determine the involved cellular and molecular mechanisms by testing the hypothesis that NT induces LTE of neuronal excitability and facilitates spatial learning and memory via NTS1/PLC/PKC-dependent inhibition of TREK-2 channels. Aim 1 will identify mechanisms underlying NT-induced LTE of neuronal excitability in the EC. We will identify the roles of PKC isoforms, PKC phosphorylation sites in TREK-2 channels and PKC- dependent phosphorylation of TREK-2 channels in vivo in NT-mediated LTE in the EC. Aim 2 will determine the mechanisms whereby NT facilitates spatial learning and memory by testing the hypothesis that NT augments spatial learning and memory via activation of PLC and PKC pathway resulting in inhibition of TREK-2 channels in the EC by using both pharmacological approach and knockout mice. Aim 3 will identify effects of NT and PD149163, a small molecule NTS1 agonist that can penetrate the blood-brain barrier on spatial learning and memory in APP/PS1 mice, an AD mouse model. We expect to determine the cellular and molecular mechanisms whereby NT facilitates spatial learning and memory and identify a novel approach of using NTS1 agonists for AD therapy in AD mouse model.